Combustible gas indicators operate by drawing an air sample into the instrument
Direct Answer
Option D: over an electrically heated platinum filament
Combustible gas indicators (explosimeters) utilize a Wheatstone bridge circuit. An air sample is drawn over an electrically heated platinum filament; the combustion of flammable gas on the filament increases its temperature and resistance, which is then measured and displayed as a percentage of the Lower Explosive Limit (LEL).
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Detailed Explanation & Context
Combustible gas indicators (explosimeters) utilize a Wheatstone bridge circuit. An air sample is drawn over an electrically heated platinum filament; the combustion of flammable gas on the filament increases its temperature and resistance, which is then measured and displayed as a percentage of the Lower Explosive Limit (LEL).
Relevant Framework: STCW 2010 Manila Amendments • DG Shipping E-Learning & Exit Exam Standards • Advanced Training for Oil Tanker Cargo Operations (TASCO).
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